10. The diameters of circles (in mm ) drawn in a design are given below:
Diameters
33−36
37−40
41−44
45−48
49−52
No. of circles
15
17
21
22
25
Calculate the standard deviation and mean diameter of the circles.
[ Hint First make the data continuous by making the classes as 32.5-36.5, 36.5-40.5, 40.5-44.5, 44.5-48.5, 48.5-52.5 and then proceed.]